Flat computer. Show that you can draw any circuit as an interconnected set of gates in the plane with no crossing wires. It suffices to draw a crossover circuit that uses gates to implement crossing...

Flat computer. Show that you can draw any circuit as an interconnected set of gates in the plane with no crossing wires. It suffices to draw a crossover circuit that uses gates to implement crossing wires: a circuit built from gates with no internal wire crossings that takes an input x at left and an input y at the top and produces as output x at the right and y at the bottom.